Insecticidal activity of the crude ethanol extract of Persea americana (Lauraceae) on larvae and pupae of Aedes aegypti (Diptera, Culicidae)

Abstract

In the search for new alternatives for control of Aedes aegypti, in view of its resistance to chemical insecticides in use, research on plant substances has been increasing due to their degradable quality and reduced toxic effect in vertebrates. The aim of this study was to evaluate the insecticidal effect of crude ethanol extract (cee) of the Persea americana Mill bark, on larvae and pupae of Ae. aegypti in the laboratory and field. The test solution was obtained by dissolving the cee in dimethyl sulfoxide
(DMSO). For each test and repetition, both in the laboratory and field, 100 larvae of the 1st, 2nd, 3rd, and 4th instars and 100 pupae were used. The same amount of larvae and pupae was used for the positive and negative control groups, performed respectively with temephos at 1 ppm and 1.6% of the DMSO treated extract. Both the laboratory bioassays and field assays were conducted using common urban breeding spots: tire, glass, and plastic. The results showed insecticidal activity of the P. americana cee on Ae. aegypti larvae and pupae, both in the laboratory and field. There was 100% mortality of the larvae of the 1st and 2nd instars at a dose of 5 ppm in the laboratory and at a dose of 10 ppm in the field. In the laboratory, the LC50 and LC90 were respectively, 7.2 and 19.3 ppm for 3rd instar, 6.6 and 15.4 ppm for 4th instar, and 93.6 and 158.7 ppm for pupae. Following the same order, in the field, the LC50 and LC90 were 27.8 and 51.3 ppm for the 3rd instar, 23.8 and 46.9 ppm for the 4th instar and 145.3 and 261.9 ppm for the pupae. The most important factor of this study was the pupicide effect of P. americana because it is very rare to find this effect from other products, either natural or synthetic. Acute oral toxicity were conducted in rats with the cee and this plant was proved to be nontoxic according to norms for products of plant origin (Acute Toxic Class Method - OECD 423).